x5 lost power

[nebilex]

Hi everyone. I was taking the x5 to the indy and I was at the traffic light and all of a sudden, I hear this "poof" sound and lost all electrical power, (radio, dash light, can't roll down window) the engine didn't shut off but it went into limp mode. The battery light, abs etc lights came on, I am not sure what's going on... I limped over to the indy and shut it off but then it wouldn't start back. I haven't heard back from the indy yet but a couple of things I suspect:
- Loose battery connection (haven't touched the battery in the past 3 years so not sure how it could get loose)
- Alternator (there was no sign of the alternator going bad, so can't see how it could just die)

Let me know what you think...

Update from Indy:
Alternator stops charging when the engine gets hot. I think he said the voltage regular may be bad.

Is it possible to rebuild these alternators or just change the voltage regulator on them? New alternator is upwards of $200.

thanks